Electromagnetic fuel injectors

ABSTRACT

In an electromagnetic fuel injector the armatures are unstuck by inducing into the magnet a neutralizing field.

United States Patent Ciroiiet et a1.

[451 May 14, 1974 ELECTROMAGNETHC FUEL INJECTORS inventors: Maurice Choiiet; Francois Denmat, both of Nantes, France Assignee: Societe Financiere lEt llndustrieiie Des Ateliers, Nantes, France Filed: June 119, 11972 Appl. No.: 264,329

[30] Foreign Application Priority Data July 1, 1971 France 71.24083 .U-S. Cl. 123/32 EA, 317/1555, 317/D1G. 4,

, 123/32 AE Int. Cl. F02m 51/00 Field of Search 317/1555, DIG. 4, DIG. 6;

' I 123/32 EA References Cited I UNITED STATES PATENTS 2,289,059 7/1942 McNairy 317/1555 2,450,904 10/1948 Moncrief 317/1555 2,468,308 4/1949 Schwartz 317/1555 2,918,911 12/1959 Guiot 123/32 EA 3,021,454 2/1962 Pickens 317/D1G. 4 3,064,165 11/1962 Kennedy..... 317/D1G. 4 3,267,482 Moore 317/D1G. 4

Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort Flint irorney, Ager z n or Firm-Stevens, Davis, Miller &

Mosher ABSTRACT In an electromagnetic fuel injector the armatures are unstuck by inducing into the magnet 21 neutralizing fieldl r 2 Claims, 4 Drawing Figures INJECTION -15 CONTROL INJECTION --7 PATENTEBIAHMBN 3.810.449

SHEET 1 OF 2 "g3$Lg[' 5 INJEcTIoN 7 9 SIGNAL DELAY AMPLIFIER GENERATOR COUMPTER SHUNT MONOSTABLE AMPLIFIER INJECTION 5 INJECTION --7 CONTROL DELAY AMPLIFIER COUMPTER ll I7 -|3 -|5 SHUNT MONOSTABLE MONOSTABLE AMPLIFIER ELECTROMAGNETIC FUEL INJECTORS This invention relates to electromagnetic fuel injectors, of use more particularly in high-power diesel engines such as are used in ships, power stations, etc.

In engines of this kind, several cubic centimeter of fuel per cycle have to be injected in something like a few milliseconds. The moving members needed are therefore large and heavy and require considerable driving forces for the necessary accelerations. Another factor in these injectors is back electromotive force, hereinafter called back EMF, found elsewhere only in large lifting electromagnets and a few very special applications where, contrary to what happens with injectors, the speed with which the magnetic attraction increases or decreases is unimportant. In injectors, the needle providing release or closure of the injection orifice must rise and fall very rapidly so that the curve representing needle movement plotted against time is rect angular i.e., very similar in shape to a castellati'on. The curve representing the magnetic field strength of the electromagnet winding plotted against time, should therefore have a similar shape. Unfortunately, back EMF effects oppose rapid growth and decay of the field.

It is an object of this invention to provide a process helping to speed up decayof the field from maximum to minimum strength. 7'

In an injector for high-power applications, the spring which keeps the needle closed applies a force of several hundred kg. An opposing but appreciably smaller force arises from the fuel pressure and varies according as the needle is in the raised or lowered position. The attraction operative on the magnetic shunt rapidly secured to the needle exceeds the difference between the two forces just mentioned by an amount which defines the acceleration of the moving masses at the beginning of the rise. Although the air gap is small to start with, the attraction increases considerably, to become very high indeed when the armatures are in engagement with one another.

Rupturing of the current must be instantaneous if the needle is to drop very rapidly. The back EMF produced in the winding means that protection in either mechanical or electronic form must be provided for the rupturing or make-and-break device. A circuit-closing diode seems the best idea but has the disadvantage of providing no energy recovery. Consequently, the curve representing current flow through the winding has a rapid drop after rupture, followed by a fairly long phase in which the current decreases much more slowly. The reduced current is nevertheless capable of keeping the needle raised for an appreciable time, since the armatures are sticking.

To obviate this disadvantage, it is known to maintain a small air gap between the stationary and moving armatures during the rise of the needle. This step, as well as being difficult to embody, due to the forces being very high and to the need for rapid movement of heavy parts, has the disadvantage of correspondingly increasing the attraction distance between the armatures and therefore of further increasing the field strength needed for a given acceleration at the start of the auxiliary winding in addition to the main winding and by causing an opposing current, of adequate strength and oppositely directed to the field to be cancelled, to flow through the auxiliary winding at the time of rupture. For optimum results, the strength of the current through the auxiliary winding, the time at which such current arises and the duration of such current are variable.

The following description, taken together with the accompanying exemplary non-limitative drawings, will show clearly how the invention can be carried into effeet.

In the drawings:

FIG. 1 is a diagram of a first embodiment of the invention;

FIG. 2 is a graph, with time plotted along the abscissa and current along the ordinates, showing the shape of the signals or pulses used in the embodiment of FIG. ll;

FIG. 3, is a diagram of a variant having provision for altering the timing of the signal transmitted to the auxiliary winding, and

FIG. 4 is a graph which supplements the graph shown in FIG. 2 and which shows the shape of the signals used in the variant of FIG. 3. 1

In the embodiment shown in FIGS. 1 and 2, an electromagnet ll of an electromagnetic injector and an armature 2 associated with an injector needle (not shown) are conventional items and are therefore shown in only very diagrammatic form.

The electromagnet 1 has a main winding 3 and an auxiliary winding 4 which is equal or equivalent to the main winding except for its direction. Main winding 3 is energized via a circuit comprising an injection control signal generator 5 which transmits signals, as shown on line A in FIG. 2, to an injection delay computer 7 determining, in dependence upon various engine'operating parameters, the transmission of square or rectangular signals 8 represented by a line B in FIG. 2. Signals 8 are amplified by an amplifier 9 which out puts distorted control signals 10, as indicatedby a line C in FIG. 2, to the main winding 3 so as to attract armature 2 and therefore raise .the injector needle.

' The leading edge of the square signal 8 is detected by such signal being sampled between computer 7 and amplifier 9 and supplied to a shunt device 11, the same outputting a signal 112, of the shape represented by a line D in FIG. 2, to a monostable 13 adapted to output a square or rectangular signal 14 (line E in FIG. 2) whose leading edge coincides with the trailing edge of signal 8 and whose length can be as required. Signal 14 goes to the auxiliary winding 4 viaan amplifier 15 which is similar to the amplifier 9 and which outputs the opposing distorted signal 16 (line F in FIG. 2).

Consequently, one of the decaying parts of the control signal flows through the main winding 3, the growing part of the opposing signal 16 flows through the auxiliary winding 4, so that the resulting field of the electromagnet l is cancelled very rapidly and. the armature 2 drops very fast, so that a return spring (not shown) can return the needle to its closed position.

In the variant shown in FIGS. 3 and 4 the main winding 3 is energized as just described, but a monostable l3 determining the length of the signal 14 transmitted to the amplifier l5 and thence to the auxiliary winding 4 (lines H and I in FIG. 4) is preceded by a further monostable l7 outputting a square or rectangular signa] 18 whose leading edge coincides with the signal 12 and whose trailing edge coincides with the leading edge of signal 14; consequently, the timing of the signal 14 and therefore of the action of the opposing signal 16 on the auxiliarywinding 4 can be shifted. This double adjustment feature improves the flexibility of adaptation of the facility to individual requirements.

The invention is very useful for fuel injection devices in heavy diesel engines such as are used in ships, power stations, factories, etc.

We claim:

1. Apparatus for accelerating unsticking of stationary and moving electromagnet armatures in an electromagnetic injector, comprising:

an injector control signal generator;

an electromagnet having a main winding for receiving signals from said signal generator, and an auxiliary winding for receiving opposing-signals;

a computer connected to said signal generator for outputting square or rectangular signals to the main winding;

an amplifier connected between said computer and said main winding;

means for supplying the auxiliary winding with an opposing signal immediately upon cessation of a control signal from said signal generator, said means comprising:

means for shunting the trailing edge of a control signal from said computer, a first monostable connected to said shunting means for producing a square or rectangular signal of a required length,

a second monostable in series with said first monostable for adjusting the start of the square or rectangular signal produced by said first monostable, and an amplifier connected between said monostables and the auxiliary winding for transmitting a square or rectangular signal to said auxiliary winding.

2. The apparatus of claim 1 wherein said windings have different directions, but are otherwise identical. 

1. Apparatus for accelerating unsticking of stationary and moving electromagnet armatures in an electromagnetic injector, comprising: an injector control signal generator; an electromagnet having a main winding for receiving signals from said signal generator, and an auxiliary winding for receiving opposing signals; a computer connected to said signal generator for outputting square or rectangular signals to the main winding; an amplifier connected between said computer and said main winding; means for supplying the auxiliary winding with an opposing signal immediately upon cessation of a control signal from said signal generator, said means comprising: means for shunting the trailing edge of a control signal from said computer, a first monostable connected to said shunting means for producing a square or rectangular signal of a required length, a second monostable in series with said first monostable for adjusting the start of the square or rectangular signal produced by said first monostable, and an amplifier connected between said monostables and the auxiliary winding for transmitting a square or rectangular signal to said auxiliary winding.
 2. The apparatus of claim 1 wherein said windings have different directions, but are otherwise identical. 